Three Maltese men have been charged for the murder of Daphne Caruana Galizia, the investigative journalist who was killed by a car bomb last month.

The three suspects include two brothers, George and Alfred Degiorgio, and Vincent Muscat. The suspects were also charged with criminal use of explosives, being involved in organised crime, and criminal conspiracy.

All three pleaded not guilty to the charges at a hearing late on Tuesday.

Joseph Muscat, Malta’s prime minister, promised in a press conference on Monday that he would not leave any stone unturned in finding who ordered the journalist to be killed and who carried out the attack. Muscat was a common subject for Caruana Galizia, who was a relentless campaigner against corruption in Malta.

‘The situation is desperate’: murdered Maltese journalist’s final written words

Caruana Galizia’s family has filed a legal claim against Malta’s police force and has alleged that the investigation has not been independent or impartial, because of connections between a senior police investigator and a government minister. Both were subjects of Caruana Galizia’s blog.

The police said on Tuesday night that an unspecified number of other suspects who were arrested on Monday would be released on bail.

Searches that were conducted during dawn raids had yielded a number of items that would help with ongoing investigations, the police said. The investigation was also aided by the FBI, Europol, and the National Investigations Bureau of Finland.

There were no new details about how the three suspects might be connected to the crime or the evidence that has been collected against them.

According to a report in the Times of Malta, Vince Muscat, one of the alleged killers, was known to police because of previous legal altercations. George Degiorgio was previously charged in court with possession of unlicensed firearms, drugs and tools that could be used to pick locks. The newspaper also reported that investigators had allegedly focused on the suspects because of telephone intercepts, including from a mobile phone that allegedly triggered the bomb.

The most significant investigations by the murdered journalist stemmed from the Panama Papers, a leak of documents from the archives of the offshore law firm Mossack Fonseca.